Harcourts Australia said written sales in March were 8 per cent higher than the previous record result, set in November 2013.
Settled sales were also 3 per cent higher than the previous best month, December 2014.
Results in NSW were particularly strong, with written sales up 41 per cent year-on-year and settled sales up 35 per cent.
NSW chief executive Mark Morrison said growth has been particularly strong in the north-west and south-west of Sydney.
Mr Morrison said it had been clear that housing values would rise in those areas from a combination of affordable family housing and the construction of new infrastructure.
“We were really poised to take advantage of what we saw as an up-and-coming area and that has largely contributed to our success,” he said.
National operations manager Marcus Williams said there had also been significant growth in other states and in other parts of the business.
“In March we’ve seen growth across New South Wales, Victoria, Tasmania and in both our commercial and regional and rural arms, NAI Harcourts and Landmark Harcourts,” Mr Williams said.
In the 12 months to 31 March 2015, NAI Harcourts opened 13 new locations, with written sales up 78 per cent and settled sales up 14 per cent, according to the group.
Landmark Harcourts achieved record settled sales for March, with settlements up 17 per cent from the year before.
[Related: Harcourts opens 53 new offices in 12 months]